This is almost all true, but KDE is worthy because it proves that Qt and its "parts" are up to the task of hosting an environment - it also manages to exist in Windows with its threads and in X. Think of Qt as the PM level X interface for the port.
You don't need to port the code, you need to port the functionality.
What about the GNUStep environment? I know nothing. Would that be a hospitable place for WPS?